Timecode fail with fast backspin

[Ambrosio Barceló]

When I do a fast backspin with a vinyl control, the position is wrong: it seems that Mixxx miss some of "all the way" with a fast timecode playing.

Here is a video with an example, and I attach an audio with similar backspins like with Mixxx in the video.

https://www.youtube.com/watch?v=M1h2go2fH90

[Ambrosio Barceló (bronxio)]

I attach this as well, just in case that there's something different (but I guess not)

[Be (be.ing)]

Can anyone confirm this with other types of control vinyl?

[Ambrosio Barceló (bronxio)]

I've just ordered a Serato Control Vinyl (CV02, the recommended one by Xwax). So I guess that in two weeks more or less (maybe "more more than less") I'll be able to test it with it as well.

When I was living in another city, I tested a previous version of Mixxx (the last official release before 2.0.0, I guess, about February 2016) with two MixVibes timecode vinyls (my actual one is one of them) and a Serato one, borrowed from a friend. I have the "emotional memory" of failing both types in precision with Mixxx because fast spins, but let's confirm that my memory serves me correctly...

I was testing some more with the MixVibes one, and found a February 2016 video recording test with the same MixVibes Cross version and different soundcard and PC. I realized that in the 2016 recording Cross is very less precise. Maybe because a poorer hardware? I don't know if it could be because a wrong setup (but I don't know anything new about Cross setup now, and I tested it today with 256 a 512 buffer sizes, I bet I never used higher or lower ones). But just in case, I tested again Cross now just to be sure that it's working ok, and found that with a very fast spin it miss, exactly, one spin: https://youtu.be/Gc9hpR3Wmr8

What is more, I did manual needle drop just to show that it's always in relative mode (for discarding a needle drop problem), and I realized that Cross sometimes fails, but it's still more reliable than Mixxx: https://youtu.be/ZbQ2LA_sdXk

So, on one side, MixVibes timecode may be not optimal (proprietary software shows problems with it as well). But on the other side, Mixxx is less precise than Cross with the same system setup.

You know, I would say that the MixVibes timecode tone is too high, but here you can check how Serato, Traktor MK2 and MixVibes timecode tones sounds (quartz lock speed): https://youtu.be/uaPRSR_Iqgg

It's weird that Traktor MK2 has that high-pitched tone (the highest one of that three), but it doesn't fail like MixVibes. I saw really fast backspins with those Serato and Traktor vinyls and never, ever failed. Check this video to see very fast backspins with, exactly, that Traktor control Vinyl of the video: https://youtu.be/1holkHmEnJ0

[Ambrosio Barceló (bronxio)]

I finally got the Serato CV02!

First of all, I'm afraid that I wasn't right about the needle drop thing, so please ignore that (that's why I deleted that video). It seems that Cross keeps the rotation position, but Mixxx just maintain the track in any part of the spin (it's a different, but right way as well to do it).

So, about the fast backspin bug, I've tested them with the Serato timecode vinyl and it fails as well, as you can check here: https://youtu.be/rhxAP4juuEQ

I've tried to test it with Xwax under UbuntuStudio 16.04, but I can't find how can I "say" to Xwax (compiled for ALSA) that I want to use the channels 3 and 4 of my Z2 (stereo channel "A") instead of 1 and 2 (mic/aux, no phono preams). If anyone can help me with this, I can test it with the very same setup but the software, just to be sure that this is a Mixxx issue and not a Xwax one.

[Ambrosio Barceló (bronxio)]

Ok, I change my mind about the needle drop relevance.

Traktor and Cross software (and I'm sure that Serato as well) work in different way in relative mode: they only mind the perpendicular position to keep the song track position when they don't receive timecode signal. They don't with the rotation position (the song track position changes when the timecode signal returns and "see" that it's another vinyl rotation position). Mixxx minds the perpendicular position and the rotation position (song track position always continues exactly from the last song track position, nevermind where the needle is when the timecode signal is back). Please watch this video to see what do I mean:

https://youtu.be/EH73r8gWHLg

I think there is no advantage with the actual Mixxx way, because the big problem is a needle jump between grooves (perpendicular position), and besides, if it doesn't mind the rotation position, this backspin bug may be fixed (I bet). If there's a forward or backward jump (for example, when the needle drops and makes some little jumps until it finally get successfully into the groove), maybe the software can play it some ms more when the timecode signal dissapears (I guess that's what the other software make).

[Ambrosio Barceló (bronxio)]

"mind "and "don't/doesn't mind" must be interchanged in #6, sorry.

@daschuer what do you think about the #6 idea?

[Daniel Schürmann (daschuer)]

Yes, that sounds like a bug, it is worth to change. Isn't this a separate issue?
If yes, please copy you drscribtion to a new bug.
I hope, I will find time to look into it.

[Ambrosio Barceló (bronxio)]

I was thinking in opening a new bug because this indeed, but I wasn't sure because I think it's related with this.

I open it as a separate one then, it's a problem without fast backspins as well: https://bugs.launchpad.net/mixxx/+bug/1720462

By the way, I realized that fast backspins fail in absolute mode as well. I hope this is not a Xwax heredated problem (I can't test it under my Ubuntu with my Z2, because the channel setup problem that I mentioned above)

[Ambrosio Barceló (bronxio)]

Tested xwax under Ubuntu 18.04 and a MixVibes U-MIX44, just in case that this problem comes from there. It seems that it doesn't: xwax makes corrections automatically. In the same cases that Mixxx lose the last position in fast backspins, xwax reports "Seek to new position Xs." (X = time value) I understand that Mixxx doesn't do that, so maybe there the problem is.

You can check the video. Sorry it hasn't sound and it's some dark, but you can notice when xwax reports the corrections, and the vinyl position matches with the wave in the screen. I attach a snapshot of my terminal as well if it's hard to see.

https://youtu.be/gPc_JKbXHD0

[le3d (schock-5)]

Hello, just to let you know. I can repro this problem on a raspberry3b+ (raspberian with realtime kernel) with serato 2b discs and traktor audio 6 on Mixx2.1.6. I would like to use visual marks on the disc, rather than waveforms on the monitor.
Other than that - really great software!!! :)

[Swiftb0y (swiftb0y)]

Mixxx now uses GitHub for bug tracking. This bug has been migrated to:
https://github.com/mixxxdj/mixxx/issues/8927